Circuit arrangement for sending of current impulses over telephone lines



June 1932- R. TRECHCINSKI 1,864,381

CIRCUIT ARRANGEMENT FOR SENDING OF CURRENT IMPULSES OVER TELEPHONE LINES Filed March 3. 1927 4 sheets-sheet 1 c] 6 7 Tr 15 R. 7r'ecAcms/fl' June 21, 1932. RR TRECHClNSK] 1,864,381

CIRCUIT ARRANGEMENT FOR SENDING OF CURRENT IMPULSES OVER TELEPHONE LINES Filed March 3, 1927 4 Sheets-Sheet 2 Amen/7mg WWW,

June 1932. R R c clNs I 1,864,381

CIRCUIT ARRANGEMENT FOR SENDING OF CURRENT IMPULSES OVER TELEPHONE LINES Filed March 3, 1927 4 Sheets-Sheet 3 June 21, 1932. R TRECHCINSK] 1,864,381

CIRCUIT ARRANGEMENT FOR SENDING OF CURRENT IMPULSES OVER TELEPHONE LINES Filed March 3. 192'? 4 Sheets-Sheet' 4 Niven-far Patented June 21, 1932 UNITED STATES PATENT OFFICE ROMAN TRECHCINSKI, 0F WARSAW. POLAND, ASSIGNOR '10 TELEFONAKTIEBOLAGET L. M. ERICSSON, 0F STOCKHOLM, SWEDEN, A COMPANY OF SWEDEN CIRCUIT ARRANGEMENT FOB. SENDING OF CURRENT IMPULSES OVER TELEPHONE LINES Application filed March 3, 1927, Serial No. 172,490, and in Poland April 24, 1926.

In sending direct current impulses in rapid succession over long telephone lines one has to reckon with such disturbances which are due to the electrical properties of the line, that is to say the capacity, leakage, inductivityand resistance. Even if the impulse transmission takes place by interrupting and closing the line circuit at the sending place, it may thus occur that the current does not decrease down to zero at the receiving place but varies, during the transmission of aseries of current impulses, for instance in the, manner indicated in Figures 1 and 2. These conditions are particularly conspicuous in lines with a high self-induction, for instance in pupinized lines. From a technical point of View it is out of question to construct an impulserelay of the usual type in such a manner as to make itoperate in the desired manner under said conditions. The present invention relates to a connecting device, whereby the said disadvantage is removed, and which renders it possible in the desired manner to actuate an impulse relay by means of direct current impulses also over lines where, on account of the electrical properties, of thelines, the current at the receiving end is not reduced to zero at each interruption of the line circuit at the sending end.

The invention will be described more fully with reference to the accompanying drawings, in'which Figs. '1 and 2'illustrate the cur.- rent variations at the receiving end of a line of the, type in uestion. Fig. 3 serves to illustrate the mo e of action according to the invention. Fig. 4 is a circuit diagram according to one embodiment of the invention as applied to a line provided with a microphone feeding bridge. Fig. 5 is another embodiment of the invention in connection with a link circuit connected between the line and the receiving relay. Figs. 6 and *7 are similar applications of the invention.

Fig. 1 shows the current variations at the receiving end of a loaded line caused by five consecutive interruptions of short duration at the sending end of the line. Fig. 2 is a similar diagram show ng the current variations at the receiving end caused by ten con- PR is a polarized relay shunted through a condenser C to an ohmic resistance R included in the line branch La. The relay armature 5 is so arranged as to have a tendency to-bear normally against its back contact 6, but which may be shifted into the operative position against a contact 7 by a current flowing in the direction from 8 to 9. I

When the line circuit is closed, a current flows through the resistance R, which causes a difierencefof potential between the points 10 and '11, whereby the condenser G is charged. The. charging current flows through the polarized relay PR in the direc tion from the right to the left hand side, the armature being then retained in the inoperative position shown in the figure. When the line circuit is broken at the sending place,

the current flowing in the resistance R is decreased to Zero or to a smaller positive value; Consequently, the potential between E the points lO'and' 11' will be less. and thG'COIb denser C is discharged. The discharging current fiowsthrough therelay PR in'the direction from the left tothe right hand side, the armature 5 being then shifted to the Working contact 7. Now, if the line current is again increased by the circuit beingclosed at the sending place, the armature'b is again shifted to the contact 6. It will'thus appear that the relay PR {is brought into action by the rapid current variations caused by the current impulses in the relay circuit, but not through the absolute value of the line current nor by comparatively slow current variations, which cannot give rise to the potential difference required to shift the relay armature. In other words, the position of the relay armature is dependent on the current derivative it (it When dt is positive, the armature bears on the back contact, and when i i dt is negative, it bears on the working contact. These movements of the relay armature can be utilized directly or indirectly for the transmission of current impulses from one circuit to another in telephone plants. 7

Figures 4 to 7 show applications of the invention in automatic telephone systems and illustrate different ways of connecting the impulse relay to junction lines or link circuit provided with a microphone feeding bridge and, contingently, also with a speaking transformer and a blocking condenser. According to the invention, inductances and capacities already existing in such junction lines may be used to advantage, for the purpose of providing a suitable circuit arrangement for the relay.

In the arrangement according to Figure 4, the impulse relay PR is shunted through a condenser C to an ohmic resistance R contained in the microphone feeding bridge. The arrangement operates in principle in the way explained in connection with Fig. 3.

Fig. 5 shows the invention applied in a type of link circuit or junction line in which microphone current is supplied to the junction line onboth sides of two condensers C and C connected each in a separate line branch. In this case, the impulse relay is connected be tween the two line branches behind the blocking condensers C C counted from the sending end of the line, the source of current for the microphone being connected between the two windings of the relay.

The link circuit to which the invention is applied comprises four resistances R R R R over which microphone current is normally supplied to the junction line on both sides of two condensers C and C connected in each one of the line branches. In this case the impulse relay PR is divided into two halves, each of which is connected up between one line branch and one pole of the microphone battery. Assuming at first that the two. resistances R and R are dispensed with,

each of the halves of the winding of relay PR together with one of the condensers G or C respectively and one of the resistances R or R respectively, is connected up to the line in exactly the same manner as the relay PR as a whole in Figure 3. For instance, the left hand half of the winding of relay PR in series with the condenser C is obviouslyconnected in parallel with the resistance B In the same manner the other half of the winding is associated with the resistance R and the condenser C The resistances R and R form shunts to each one of the halves of the winding PR. The unfavorable effect of these shunts is, however, practically unimportant owing to the high values of said resistances.

In the arrangement according to Figures 5-7 the impulse relay PR is adapted, upon being operated, to interrupt a secondary line circuit comprising the branches La Lb. (Figures 5, 6) and La Lb (Figure 7) re spectively, said line circuit being normally closed through the retardation coil Si, the contact 6 and the armature 5 of the relay.

Figure 6 illustrates a similar arrangement in which the impulse relay is connected up in the secondary circuit .of the speech transformer PR, the primary coil of which is connected up to the link circuit in the same manner as the winding of the relay PR in Figure 5, i. e. behind the blocking condensers counted from the sending end. It should be observed that the middle point of the primary winding of the relay PR, owing to the symmetry of the link circuit, is a neutral point and, that accordingly the said point may be connected with earth without changing the mode of operation of the arrangement. On the other hand, the said primary winding may be divided into two halves which may be connected up, similarly as the halves of the winding PR in Figure 5, to each one of the poles of the battery. The mode ofaction would in no Way be altered by such measures and may accordingly be said to be quite analogous with the mode of actionof the arrangement according to Figure 5.

Figure 7 shows a circuit arrangement analogous to that illustrated in Fig. 6 and applied to another type of trunk lines, in which the microphone feeding bridge contains the windilng of two speaking transformers Tr and I claim;

1. An arrangement for sending selecting impulses over aspeaking line including a blocking condenser in the line branches, characterized by that. the impulse relay is connected to the-line behind said condenser, counted from the sending end of the line, in

such a manner that the relay will be brought into action by rapid current variations caused in the relay circuit by theline current impulses but not through the absolute value of the line current. i

2. In an arrangement for sending selecting impulses in combination, a speakin line, means for introducing current impu ses at one end of the line, blocking condensers inserted in the line branches, and an impulse relay connected up to the line behind the blocking condensers, counted from the sending end of the line.

3. In an arrangement for sendin selecting impulses in combination, a spea in line, means for introducing current impu ses at one end of the line, blocking condensers inserted in the line branches, an impulse relay, and means for connecting up said relay to the line behind the blocking condensers, counted from the sending end of the line.

In testimony whereof I afiix my signature.

ROMAN TRECHGINSKI. 

